diff --git a/ChangeLog.txt b/ChangeLog.txt
index e725203d..1178e908 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -10,6 +10,10 @@ Broker:
 - Fix reloading of listeners where multiple listeners have been defined with
   the same port but different bind addresses. Closes #2029.
 - Fix `message_size_limit` not applying to the Will payload. Closes #2022.
+- The error topic-alias-invalid was being sent if an MQTT v5 client published
+  a message with empty topic and topic alias set, but the topic alias hadn't
+  already been configured on the broker. This has been fixed to send a
+  protocol error, as per section 3.3.4 of the specification.
 
 Apps:
 - Allow command line arguments to override config file options in
diff --git a/src/handle_publish.c b/src/handle_publish.c
index 3f9a1627..1e3d9b4f 100644
--- a/src/handle_publish.c
+++ b/src/handle_publish.c
@@ -186,7 +186,7 @@ int handle__publish(struct mosquitto *context)
 			rc = alias__find(context, &msg->topic, (uint16_t)topic_alias);
 			if(rc){
 				db__msg_store_free(msg);
-				return MOSQ_ERR_TOPIC_ALIAS_INVALID;
+				return MOSQ_ERR_PROTOCOL;
 			}
 		}
 	}
diff --git a/test/broker/02-subpub-qos0-topic-alias-unknown.py b/test/broker/02-subpub-qos0-topic-alias-unknown.py
index cdce33ce..62227127 100755
--- a/test/broker/02-subpub-qos0-topic-alias-unknown.py
+++ b/test/broker/02-subpub-qos0-topic-alias-unknown.py
@@ -14,7 +14,7 @@ def do_test():
     props = mqtt5_props.gen_uint16_prop(mqtt5_props.PROP_TOPIC_ALIAS, 3)
     publish1_packet = mosq_test.gen_publish("", qos=0, payload="message", proto_ver=5, properties=props)
 
-    disconnect_packet = mosq_test.gen_disconnect(reason_code=148, proto_ver=5)
+    disconnect_packet = mosq_test.gen_disconnect(reason_code=mqtt5_rc.MQTT_RC_PROTOCOL_ERROR, proto_ver=5)
 
     port = mosq_test.get_port()
     broker = mosq_test.start_broker(filename=os.path.basename(__file__), port=port)